1. Field of the Invention
The present invention relates to a method for dynamically allocating bandwidth in an asynchronous transfer mode—passive optical network (ATM-PON), which enables effective use of network resources and provision of various ATM services under a media access control (MAC) protocol between an optical line termination (OLT) and an optical network unit (ONU) group including a plurality of ONUs in the ATM-PON.
2. Description of the Related Art
Currently, an ATM-PON system has been set and operated as an economic network establishment technology suitable for provision of broadband services. The ATM-PON system, which is an access network, makes use of an upstream traffic multiplexing. In order to effectively perform the multiplexing function, it is necessary to introduce a MAC protocol to the ATM-PON system. In many MAC protocol proposals, a tree algorithm is proposed as an algorithm for collision resolution. On the other hand, the tree algorithm may suffer degradation in its performance if time-sensitive high-priority traffic is received.
In general, a broadband PON system is employed by a number of network providers. This broadband PON system provides services at various rates from low-speed to high-speed, which services may be low-speed synchronization services such as voice services or high-speed services such as local area network (LAN) interconnection services. Therefore, it is required that bandwidth allocation based on the MAC protocol does not cause service performance degradation.
The PON system employs an optical distribution network (ODN) which is an distribution network between ONUs and a Fiber To the Home (FTTH) or Fiber To the Office (FTTC) subscriber access nodes. All nodes in the PON system are configured using a bus or tree topology.
The PON system includes the ONUs and an OLT in order to access an optical access network. The ONUs are installed in homes or office buildings, respectively. The OLT is installed in a central office and connected to each of the ONUs through an optical cable. The PON service can provide through the OLT various services including an Internet service, a plain old telephone service (POTS), a video on demand (VOD) service and the like.
In the PON system, exchange equipment and optical resources can be shared by users, and the optical distribution network is passive. Therefore, the PON system is advantageous in that its maintenance cost is low, and it is possible to easily add or delete a split due to its highly flexible structure. Further, the PON system provides a very efficient resource sharing, so that the users can be provided with various services at low costs.
However, because a number of users share the optical resources in the PON system, there may occur collision between the users. The collision is caused often under ATM-PON environments supporting multimedia traffic environments, resulting in a degradation in performance.
As a result, there is a need for a method capable of transmitting information without collision between users and effectively using network resources in the PON system.